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December 7, 2009

Bird Courtship

Fembot helps researchers study America's most bizarre bird

"The sage grouse is the most elaborate and extreme bird we have in the United States," says Gail Patricelli, an animal behaviorist at the University of California (UC), Davis. "We're basically trying to understand why we have animals that are as amazing and beautiful as the peacocks."

Patricelli sits in front of a computer monitor that has become her digital science laboratory to study hours of bird videos that she and her team have collected over the past four years. The videos reveal incredible close-ups of sage grouse courtships.

Members of Patricelli's lab study animal communi- cation and sexual selection, with a focus on understanding the amazing diversity and complexity in animal signals. Patricelli received additional National Science Foundation (NSF) funds for this research through the American Recovery and Reinvestment Act (ARRA) of 2009, which will allow her to continue her research for another three years. Among other things, the ARRA funding will pay for the salaries of her team of post graduate and graduate students who will gain research experience in the field.

Romance on a lek

"During the breeding season, the males gather together in these open areas called leks," Patricelli explains, pointing to her computer monitor, which shows a slow motion video of a male sage grouse blowing up his chest in an elaborate courtship display. "Here, they puff up and strut around. They stake out territories. Every morning, they show up on the lek and strut all morning long, and they fight with each other to defend their territories. The females show up, often in groups, walk around on the lek and basically comparison shop."

The fights among males can be dramatic, which is evident during one of the many fights that Patricelli has caught on video. To the naked eye, the fight might look harmless, but when she slows one of the videos down to 500 frames per second--super slow motion--it's easy to see the claws of one of the males rising up in a kick boxing move and slamming his opponent in the chest, while at the same time using his beak to stab the other bird's neck and his wings to whack his rival over the head. All this in a split second!

"These guys can do a great deal of damage in the course of these fights," adds Patricelli. She and her team are studying the sage grouse as a model to better understand the evolution of animal communication.

"It helps us understand the evolution of very basic behaviors like social skills and social interactions and two-way conversations, and how these evolve by the process of sexual selection. In addition, understanding how animals court and behave can help us when these animals end up in trouble," she says.

Patricelli also hopes to better understand why the populations of these dramatic, showy birds are dwindling. Among the questions, could the birds' loss of habitat and the noise from natural gas and oil drilling be interfering with their areas of courtship? Sage grouse are found in sagebrush habitat throughout the interior west, but many of the largest leks are located in Wyoming.

It took some creativity to capture the dramatic close-ups of the birds during courtship. Each spring before the birds arrive, the research team heads to a lek in Wyoming. They set-up hidden microphones and video cameras and stake out places to watch the action.

Fembot fatale

Patricelli also came up with an ingenious way to get a bird's-eye view of male courtship displays and learn how males interact with females during courtship. With support from NSF, she built a life-size female sage grouse and filled it with recording gear. She calls it a 'fembot.'

Patricelli lifts the top half of the fembot revealing a small audio recorder; a microphone that pokes-up beside fembot's neck and a tiny video camera nestled in her breast. With a remote control, the fembot is rolled out on a small train track also set-up on the lek during the mating season. When the fembot moves her head from side to side, it is apparently enough to get most males to come a courtin'.

Sounds on the lek

Sage grouse are related to chickens but the sounds made by a male sage grouse during courtship are truly unique. Alan Krakauer, a behavioral ecologist at UC Davis, scrutinizes the hours of sound recordings the researchers have collected on the lek to isolate each male's sounds. He's trying to understand if there's something in the pitch, rhythm or volume that works to attract a female.

"During courtship, the males' mouths are closed and they're using their vocal sacs to help get the sound out to the females," says Krakauer.

"The sage grouse are similar to frogs in the sense that they puff up a vocal sac at the same time they produce their vocalization, and the sound actually doesn't come from the beak; it comes through the skin of the vocal sacs," explains Patricelli. "They move their wings across the feathers on their chest and that makes a swishing sound, and that's followed by what we think are sounds produced by the syrinx, which is the bird's equivalent of a larynx."

Courtship failures

The reason why fembot is such a success in attracting males is that male sage grouse aren't picky in the least. They just want to mate as often as possible with any female they can get. It's the females who are the choosy ones, and surprisingly for many males, the dramatic song and dance appears to be in vain. Researchers are discovering that these picky females turn down most suitors.

Patricelli says only about one in ten male sage grouse will mate in a given season. Apparently, females tend to gravitate toward one male--the one with the right strut. One day, these researchers hope to know exactly what that looks like. "Our top male in one of our years of study mated 47 times during the breeding season and most males don't mate at all," adds Patricelli.

So it appears that most of the males do have reason to grouse!

The research in this episode was funded by NSF through the American Recovery and Reinvestment Act of 2009.

Miles O'Brien, Science Nation Correspondent
Ann Kellan, Science Nation Producer

Any opinions, findings, conclusions or recommendations presented in this material are only those of the presenter grantee/researcher, author, or agency employee; and do not necessarily reflect the views of the National Science Foundation.